1. Field of the Invention
The present invention relates to a system for providing oil, and, in a specialized case, a pressurized oil control signal to a variable camshaft timing system of an internal combustion engine.
2. Disclosure Information
Variable camshaft timing (VCT) has been employed for some years with various vehicular engines. Of course, the term xe2x80x9cvariablexe2x80x9d implies that the camshaft timing is changed with respect to the rotational position of the engine""s crankshaft. This means that some accommodation must be made to allow the drive sprocket or hub of the camshaft to change its phasing with respect to the body of the camshaft itself. One way to accomplish this is to provide a hydraulic adjusting mechanism having a vane type of adjuster as known to those skilled in the art and suggested by this disclosure. Yet other types of hydraulically controlled VCT devices are known to those skilled in the art and suggested by its disclosure. Regardless of the type of hydraulic device used, it is necessary to input an oil pressure signal to the device to achieve the desired camshaft phase change. Feeding oil, or more specifically, a controlled oil flow, into the front of a variable camshaft timing mechanism is broadly old in the art. U.S. Pat. No. 5,474,038 discloses a system in which a rigid cam cover is machined to fit the remainder of the front cover of an engine so as to provide a well-guided oil supply spud which is by necessity centered within the rotating hub of the VCT mechanism. Oil feed systems of the type shown in the ""038 patent suffer from the drawback that they offer utility only at a very high expense of machining and with the need to have a rigid cover which is precisely matched to the front cover of the engine. This results in a great deal of added expense for the engine manufacturer.
A system according to resident invention provides excellent control oil feed supply to a VCT mechanism without the need for precision machining of the engine""s front cover, or for that matter more than a modicum amount of precision machining in the oil feed bracket itself.
An oil feed system for an internal combustion engine having variable camshaft timing includes a bracket attached to the front structure of the engine at a final location which is determined at least in part by the interaction of the bracket and the camshaft adjuster to which it is furnishing oil. The oil feed system further comprises an oil feed spud carried on the bracket and integral therewith. The spud is registered into a bore formed in the camshaft mechanism which is being furnished with oil, so as to locate the bracket with respect to the camshaft mechanism. According to another aspect of present invention the oil supply spud preferably comprises a plurality of lands and oil seals, with lands having different outside diameters such that the land with the greatest diameter will ablate as a result of elastic bending of the camshaft caused by tension within a camshaft drive chain.
An oil flow control valve is attached to the bracket of the present oil feed system, so as to allow a flow of engine oil through the spud. The oil flow control valve may comprise a solenoid actuated valve drawn from the many types of valves known to those skilled in the art and suggested by this disclosure.
An oil feed system according to present invention may further comprise a timing chain guide which is integral with the bracket attached to the front structure of the engine.
According to another aspect of the present invention, a method for mounting a combination camshaft drive chain guide and variable camshaft timing control oil feed having an integral oil feed spud, comprises the steps of placing the oil feed spud into circular registry with a bore formed in the camshaft drive concentric with the axial centerline of the camshaft, and rotating the combination camshaft drive chain guide and camshaft timing control oil feed about the axial centerline of the camshaft and into registry with mounting provisions formed in the front structure of the engine. Thereafter the combination drive chain guide and camshaft oil feed is mounted to the front structure of the engine using the mounting provisions formed in the front structure engine. A method according to present invention may further comprise the step of starting the engine or otherwise motoring or operating the engine so as to ablate a portion of the oil feed spud as a result of the bending of the camshaft caused by the tension of a camshaft drive chain.
It is an advantage of the present invention that an oil control feed may be applied to a variable camshaft timing mechanism without the necessity of dowels or other precision machined parts to locate the oil feed structure in its entirety.
It is yet another advantage of the present invention that a VCT mechanism having an oil control system may be more compact because it is not necessary to incorporate a large front cover having the VCT oil feed build therein.
Other advantages as well as objects and features of the present invention will become apparent to the reader of this specification.